1. Field of the Invention
The present invention relates generally to automotive air temperature sensors. More particularly, the present invention relates to a method and system for diagnosing a vehicle temperature sensor.
2. Discussion of the Related Art
In the automotive industry, vehicles are typically designed to include many sensing components, modules, and systems. These sensing systems provide feedback regarding various conditions and parameters within the vehicle. Among the parameters being sensed are temperature, fluid level, and revolutions per minute (RPM). Temperature sensors typically report temperature information back to controllers within the vehicle to prevent overheating, as well as provide enhanced engine control. For example, temperature information regarding liquids such as engine coolant is desirable to prevent overheating. Similarly, information regarding air temperature at certain points in the vehicle allows engine control systems to be more accurate.
Air temperature sensors can be placed in various locations throughout the vehicle such as on the intake manifold for small vehicles, in the bumper of large vehicles for ambient temperature sensing, and over the vehicle bus. Air temperature sensors can also be modeled from other known parameters within the vehicle.
A common concern with automotive air temperature sensors relates to diagnosis of sensor rationality. For example, an intake sensor may be "stuck" such that the A/D converted signal remains unchanged regardless of the actual intake air temperature. Such a condition would be difficult to detect through the standard shorted high and shorted low electrical checks performed in the industry. It is therefore desirable to provide a diagnosis system which can detect stuck sensors. While attempts to diagnose stuck sensors have been made, certain problems still remain. One difficulty is that conventional approaches have determined a defective sensor to be one which does not change as expected over a given period of time. One shortcoming with this approach is that it fails to fully take into consideration operation of the vehicle. For example, a strictly time based sensor diagnostic system would be unable to distinguish between a vehicle which has been merely started and a vehicle which has actually been driven. Thus, the potential for incorrect fault determinations is relatively high for time based sensor diagnostic systems. It is therefore desirable to provide a non-time based system and method for identifying faulty temperature sensors without relying on expiration of time.